Metamaterial, also referred to artificial electromagnetic material, usually appears in various science literatures recently, as a new academic term for the physics field in 21st century. Three important characteristics of the metamaterial include:                1) The metamaterial is usually a compositive material having a novelty artificial structure;        2) The metamaterial has supernormal physical character (the character is not often included in the natural material);        3) The character of the metamaterial is not often decided by the nature character of the component material, but mainly decided by the artificial structure thereof.        
That is to say, the metamaterial is a material that has artificial structures as the basic unit and spatially arranged in a specific way. And the metamaterial is a new type of material having a special electromagnetic effect which is characterized by the character of the artificial structures thereof. By sequentially designing the structure of the critical physical scale of the material, the limitations in some apparent laws of the nature can be broken through, to achieve an extraordinary material function which is beyond the inherent ordinary character in the nature.
The metamaterial includes the artificial structure. Wherein, the electromagnetic response of the artificial structure mainly depends on the topological feature and size of the structure unit of the artificial structure.
The metamaterial also includes the host material where the artificial structure attaches to. The host materials plays a supporting role for the artificial structure, therefore it can be any material which is different from the artificial structure.
The stacking of the artificial structure and the host material can produce an equivalent dielectric constant ξ and a magnetic conductivity μ. The two physics parameters respectively correspond to the electric field response and magnetic field response. Therefore, the designation for the artificial structure of the metamaterial is the most critical step in the field of metamaterials. How to implement an artificial electromagnetic material and further improve the electromagnetic character of the conventional electromagnetic material has been a big difficult problem to the improvement of the modern technology.